Smith, who goes by Dee, picked the Cardinals over Kentucky, Miami, Missouri and North Carolina State on Friday afternoon. Farmington Hills, Mich., four-star 2016 wide receiver Desmond Fitzpatrick was the first commit of the day earlier on Friday.
The 6-foot-2, 198-pound Smith becomes the 19th commitment in the Class of 2015 for Louisville and will sign in February.
Scout.com has Smith ranked as the No. 38 outside linebacker in the '15 class. He has also played wide receiver and safety for his high school team.
His teammate and Alabama commitment, Keaton Anderson, told Scout.com last week that Smith was an under-the-radar type of guy.
"Dee Smith is what you call the overall athlete of the team, of the city...put a ball in his hands, no matter which sport it is, and he'll make it happen," Anderson said. "He has that freak-athlete about him, he doesn't even realize it. When he gets to a college, that right fit with that right coaching staff, he'll blow up. The sky is the limit for him.
"Having him in my secondary, I know that if the ball is thrown up, he'll make that play. It gives me relief. I know if I miss a tackle, he'll lay the wood. He's extremely fast to the football and has football smarts, he doesn't know how good he is sometimes."
As a junior, Smith had over 300 receiving yards and 90-plus tackles on defense. Smith has a brother, Rashawn Smith, who is a linebacker at Mississippi.